Finding perimeter when a side length is missing | Math | 3rd grade | Khan Academy

Lindsay finds the perimeter of a figure when a side length is not given.

3rd grade math on Khan Academy: We know you've been rocking through 2nd grade adding and subtracting all kinds of whole numbers (up to 2 digits, right?). That's awesome! In 3rd grade math we want you to start using bigger numbers and start multiplying and dividing, too. By the way, did you know that some numbers aren’t actually “whole?” They’re “partially whole.” We call them fractions! We want you to start playing around and having fun with those, too. There's also area, perimeter, and place value to be discovered. Whew. We have so much to do and can't wait to do it with you. Let's go!

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[thmttck]

This helped with my homework 📚

Thanks 🙏

[haveablessedday]

sounds like my science teacher that i used to have, she moved to a different school or something like that so we had a little final thing in the room over and and she gave her farewell speech. She was a good teacher

[ebonycharles]

Thank u for this I had a long time of understanding this for sea exam an understand 👍 up who watching this at quarantine

[lisacox]

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[preethijyothi]

I learned a lot from this video thank you

[keishalikestodraw]

Its been 5 years but its still usefull💖

[Idk-drht]

Bro at first I was like do I have to watch it then I understand tysm

[asheskept]

Little did I know how easy this was I keep forgetting about it 👍

[definecodm-yt]

Thank you for teaching me this, I’m in 4th grade and I was struggling with this even though I learned this in 3rd grade.

[nadia_random]

THANK you so much bc I have a test on this and i'm pretty good at math but this part of math was kinda hard so thank you very much 😎🎉🎉🤩🤩

[UltimateBargains]

Seems like Common Core in its heavy verbosity. I hope Common Core also teaches the simpler way of getting the correct answer. The example shows total operations is 5 additions in a very verbose expansion.

I simply added the two vertical sides of (7cm = 3cm + 4cm) to calculate the length of the left side, then add 9cm for the length of the bottom side (16cm = 7cm + 9cm), then double to (32cm = 2×16cm) for the perimeter. This requires that all angles are right angles (example video also requires that all angles are right angles). Total operations is 3; two additions, one simple multiplication (or one self-addition). That's how I learned it back in the 1960's era.

32cm = 2×(9cm + (3cm + 4cm)); perimeter equals double the sum of 2 adjacent sides.

[janoydacosta]

You must add It and you will get the answer

[xxBJBLSTxx]

IM ALMOST IN MIDDLE SCHOOL AND I DONT KNOW THIS 😂

[tashadaly]

I really needed this because school is doing complicated sums

[trippytheeasterrabbit]

Ugh I remember when it was this simple. Little do 3rd graders know 😪

[kristally]

I have done this like 20 days in a row

[Christy.Raynee]

Thank you so much for making these videos! You guys are awesome! I have been subscribing to you guys for a year!

[muhammadisaac]

32 centimetres
The perimeter of the first figure will be 32 centimetres

[andreac]

Thanks you save me from my HW !! Luv u ! Thanks! Now I understand my HW ! 😊😁

[cocohaven]

so why do we add one number at a time in the end? like when you added both 16's? I don't understand doing that in order to get two more numbers to add for the total answer.